The present invention relates generally to overload relays for electromagnetic contactors, and more particularly to a magnetic flux concentrator shield for use in an overload relay that minimizes cross pole magnetic flux interference in multiple pole contactor applications.
It is often times desirable in industrial applications to reduce the size of electrical devices, such as motor starters, while maintaining the rated electrical capacity. It is known to use Hall effect sensors for measuring current in a conductor when available space is critical. Multiple phase starters utilize a separate pole for each phase. Reducing the size of the contactor and overload relay of the starter reduces spacing between each pole. When sensitive devices such as Hall effect sensors are used, cross-pole magnetic flux contamination presents a problem. Magnetic flux generated by current flowing through a conductor in one pole may stray to an adjacent pole and be sensed by the Hall effect sensor in the adjacent pole, thereby affecting the accuracy and control function of the sensors and associated electronics. Therefore, it would be beneficial to have a magnetic flux shield in the overload relay that concentrates the magnetic flux generated by current through a conductor the flux straying into cent pole.